Drive for electric tuning means



Sept. 29, 1942. K. BRANDHOLT DRIVE FOR ELECTRIC TUNING MEANS -Filed July 29, 1939 fm/enfar:

Kurz Brcmdholt y Patented Sept. 29, 1942 UNITED STATES PATENT OFFICE DRIVE FOR ELECTRIC TUNING MEANS Kurt Brandholt, Berlin, Germany; vested in the Alien Property Custodian Application July 29, 1939, Serial No. 287,193 In Germany August 3, 1938 Claims.

Certain difficulties are encountered in the tuning methods employed in very large radio sets, especially in those using coil tuning. Such sets, especially receivers, are equipped with a great number of tuning means with the consequence that in order to tune the apparatus many coils must be adjusted. This large number includes many coils which to be tuned must be turned. This operation involves a succession of harmful mechanical jolts. These jolts in particular affect the tubes in which mechanical vibrations are necessarily set up in the electrodes. Such vibrations have a destructive effect on tube life as well as altering its electrical properties, for in response to such a change the tube fades out for a while after adjustment so that the set will not operate normally again until a certain period of time has elapsed.

This disadvantage is overcome by the use of the present invention. It will be assumed that the coil drum which serves for tuning adjustments is set in motion by a tuning operation. This operation is to be effected by a gear train, which has a variable transmission ratio, which may, for example, be accomplished by elliptical or other odd-shaped gears; and it is so designed that by a change of the transmission ratio from step-down to step-up to step-down position again the drum reaches a position of rest, the momentum acquired by the drum while the high gear ratio is effective being gradually reduced as the effective gear ratio becomes lower.

My invention will be more fully understood when considered in conjunction with the following description and drawing, of which the figure shows a preferred embodiment of the invention. In this illustration a coil-drum I carrying a plurality of coils 20A20D is shown to be geared through a gear train 2, 3, 4, 5, and a toothed disc 6 operates to apply contacts I to the difierent coils for different positions of the drum, in the desired circuit such as the tuning condenser. These contacts I can be controlled by an insulated spring contact support 8. Tension from the spring l0 forces a ratchet arm 9 to follow the recesses of the disc 6.

At the same time as this operation is being effected, a change is likewise being made from one goniometer range to another by switch 13 controlling the circuit for goniometers G1 and G2. By this switching arrangement the frequency range of the goniometers may be brought into suitable relation with the circuit tuned by the coils 2UA--20D. This other change is initiated in a gear 2 meshing another gear I I, is then translated by a Geneva movement 12 through a cam Hi to goniometer control contacts [3. Driving the coil-drum in conjunction with the range control of the goniometer occurs only when the elliptical shaped gear 5 is turned through 360 degrees. As the illustration shows the gear train begins with a large gear ratio. In this position it is able to exert a large torque which is a factor important in turning the drum out of a ratchet setting. The gears change their transmission ratio from small to large, and the drum after unratcheting enters into the next sphere of operation. The momentum of the drum is also used at the same time for operating the goniometer control contact, and in a reverse operation this acts as a brake upon the drum. As the drum nears its new position the gear ratio between 5 and 4 again becomes large tending to slow down the coil drum so that a shock is not transmitted to the radio set.

A further feature of the invention is that the contacts I are removed from the drum until a setting is made. This is accomplished with the ratchet arm 9, which lifts the contact supports 8 so that the contacts are removed by the strength of their own springs. This arrangement thus avoids contact wear due to sliding friction.

What is claimed is:

1. A radio apparatus employing coils for tuning, comprising carrier means carrying a plurality of coils, adjusting means for moving said carrier means into different positions to render a desired one of said coils effective, said adjusting means comprising a drive mechanism for rotating said carrier means, and eccentrically mounted rotary control means operative to render said rotary movement slow upon initiation of rotation, more rapid during an intermediate portion of its rotation and slow again upon its approach to said adjusted position.

2. In radio apparatus as in claim 1, wherein said last named means comprises an elliptical gear train to effect a gear ratio variation from step-up to step-down and back again to step-up by one control operation.

3. In radio apparatus employing coils for tuning and contacts for connecting such coils to external circuits, mechanical means for adjusting said tuning coils with a variable transmission ratio varying from low ratio, to higher ratio, to lower ratio for each adjustment, insulated spring contact supports controlled by said mechanical adjusting means and means for raising said contacts during said adjustment.

4. In ratio apparatus according to claim 3,

wherein said last named means comprises ratchet means operatively associated With the said coils to effect the said control.

5. In radio apparatus employing coils for tuning, and goniometer circuits, mechanical means for adjusting said tuning coils with a variable transmission ratio which varies from low, to higher, to low during an adjustment, means such as a Geneva movement operatively associated with the said mechanical means for alternately rendering said goniometer circuits efiective and ineffective, and means for utilizing the momentum of the said coils generated during adjustment to facilitate operation of said Geneva movement.

KURT BRANDHOLT. 

